A spark plug used for a combustion apparatus of an internal combustion engine or the like includes, for example, a center electrode extending in an axial direction, an insulator provided around the center electrode, a circular columnar metallic shell assembled outside of the insulator, and a ground electrode whose proximal end portion is bonded to a front end portion of the metallic shell. The ground electrode is bent at an approximately central portion thereof such that its distal end portion faces the front end portion of the center electrode, whereby a spark discharge gap is formed between the front end portion of the center electrode and the distal end portion of the ground electrode.
In recent years, there has been disclosed a technique for improving ignition performance by providing a tip formed of a noble metal alloy on a portion at the distal end of the ground electrode, the portion forming the aforementioned spark discharge gap (see, for example, Japanese Patent Application Laid-Open (kokai) No. 2009-37750).